In our daily life, ventilation systems such as air-conditioners are commonly used in working or living spaces, e.g., office buildings and apartments, for supplying fresh outdoor air and exhausting polluted indoor air simultaneously in order for keeping a favorable and healthy environment to stay. Generally, the supplied air and the exhausted air have different temperatures and humidities. In this connection, a significant effect of energy saving could be expected if the exchange between the indoor air and the outdoor air can be achieved not only in heat but also in moisture. In order to satisfy such requirements, total heat exchangers are developed. A total heat exchanger is capable of exchanging sensible heat (temperature) and latent heat (moisture) simultaneously between different types of airflows without mixing them, and therefore is an effective means for saving energy by recovering both sensible energy (temperature) and latent energy (moisture) between the airflows.
A total heat exchanger generally employs a heat exchanging element as a tool, through which both the supplied air and the exhausted air pass and by which the exchange of heat and moisture between the airflows is carried out. If the exchanging element employed is a rotary heat exchange wheel, then the total heat exchanger using the rotary wheel is typically referred to as “rotary-type total heat exchanger”. Generally, a rotary wheel is constructed in the form of mesh-like or honeycomb structure which is comprised of a matrix or media of heat exchange material (capable of absorbing thermal energy) coated or impregnated with a hydrophilic material (capable of absorbing moisture), wherein the heat exchange material may be, among others, metal wire, ceramic fiber, asbestos paper or fiberglass. Thus, the rotary wheel is capable of absorbing moisture and/or thermal energy from one stream and upon further rotation of the wheel, releasing the moisture and/or thermal energy to an adjacent stream. For example, in winter, the wheel can be used to recover heat and moisture from relatively higher temperature exhausted air from indoors for transfer to a cool, dry supplied air from outdoors. In a summer season, the wheel can also be applied to cool and dehumidify a hot, moist supplied air from outdoors by extracting moisture and heat energy and then transferring to a relatively cooler and drier exhausted air from indoors.
An example of a rotary wheel in a rotary-type total heat exchanger is shown in FIG. 12. The rotary wheel 1 is in a cylindrical form and has a beehive-like structure with a plurality of air passageways 2 defined parallel to the axis of the wheel 1. The wheel 1 is mounted to a frame comprised of a vertical plate 3 and a horizontal plate 4, and is maintained across a first air stream (e.g., supplied fresh outdoor air indicated by arrows E-E) and an adjacent but separate second air stream (e.g., exhausted dirty indoor air indicated by arrows F-F). The horizontal plate 4 traverses the vertical plate 3 to thereby divide the wheel 1 into two semi-circular portions. The supplied air and the exhausted air flow respectively through the two portions of the wheel 1 in a counter-current manner to exchange heat and moisture between them by continuously rotating the wheel 1 via a motor 5 associated with the wheel 1. After this exchanging process, the amount of energy required to heat, cool, humidify or dehumidify the supplied air is accordingly reduced, thereby achieving the purpose of saving energy.
The rotary-type total heat exchanger is effective in keeping indoor air quality, as well as in saving energy, as is identified above. However, in order to exhibit its full advantages, many improvements still can be made on the design of the rotary-type total heat exchanger. For example, the supplied air and the exhausted air to be exchanged are typically directed by blowers. The airflows from the blowers flow in a direction which are not to enable the airflows to flow evenly over the air passageways 2 of the rotary wheel 1. This greatly impairs the exchange rate of heat and moisture between the airflows. Moreover, the exchange of sensible heat between the airflows is conducted only by resorting to the heat-conductivity capacity of the heat exchange material used in the wheel 1, which limits the sensible heat exchange rate between the airflows.
In view of the above-mentioned disadvantages of the conventional rotary-type total heat exchanger, there is a need for a rotary-type total heat exchanger which can distribute airflows to be exchanged more evenly over air passageways of its rotary wheel. What is also needed is a rotary-type total heat exchanger which can improve the sensible heat exchange rate between the airflows conducting heat exchange in the rotary-type total heat exchanger.